Double incretin receptor knock-out (DIRKO) mice present with alterations of trabecular and cortical micromorphology and bone strength.

A role for gut hormone in bone physiology has been suspected. We evidenced alterations of microstructural morphology (trabecular and cortical) and bone strength (both at the whole-bone - and tissue-level) in double incretin receptor knock-out (DIRKO) mice as compared to wild-type littermates. These results support a role for gut hormones in bone physiology. INTRODUCTION: The two incretins, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), have been shown to control bone remodeling and strength. However, lessons from single incretin receptor knock-out mice highlighted a compensatory mechanism induced by elevated sensitivity to the other gut hormone. As such, it is unclear whether the bone alterations observed in GIP or GLP-1 receptor deficient animals resulted from the lack of a functional gut hormone receptor, or by higher sensitivity for the other gut hormone. The aims of the present study were to investigate the bone microstructural morphology, as well as bone tissue properties, in double incretin receptor knock-out (DIRKO) mice. METHODS: Twenty-six-week-old DIRKO mice were age- and sex-matched with wild-type (WT) littermates. Bone microstructural morphology was assessed at the femur by microCT and quantitative X-ray imaging, while tissue properties were investigated by quantitative backscattered electron imaging and Fourier-transformed infrared microscopy. Bone mechanical response was assessed at the whole-bone- and tissue-level by 3-point bending and nanoindentation, respectively. RESULTS: As compared to WT animals, DIRKO mice presented significant augmentations in trabecular bone mass and trabecular number whereas bone outer diameter, cortical thickness, and cortical area were reduced. At the whole-bone-level, yield stress, ultimate stress, and post-yield work to fracture were significantly reduced in DIRKO animals. At the tissue-level, only collagen maturity was reduced by 9 % in DIRKO mice leading to reductions in maximum load, hardness, and dissipated energy. CONCLUSIONS: This study demonstrated the critical role of gut hormones in controlling bone microstructural morphology and tissue properties.

MHC Class II Transactivator Is an In Vivo Regulator of Osteoclast Differentiation and Bone Homeostasis Co-opted From Adaptive Immunity.

The molecular networks controlling bone homeostasis are not fully understood. The common evolution of bone and adaptive immunity encourages the investigation of shared regulatory circuits. MHC Class II Transactivator (CIITA) is a master transcriptional co-activator believed to be exclusively dedicated for antigen presentation. CIITA is expressed in osteoclast precursors, and its expression is accentuated in osteoporotic mice. We thus asked whether CIITA plays a role in bone biology. To this aim, we fully characterized the bone phenotype of two mouse models of CIITA overexpression, respectively systemic and restricted to the monocyte-osteoclast lineage. Both CIITA-overexpressing mouse models revealed severe spontaneous osteoporosis, as assessed by micro-computed tomography and histomorphometry, associated with increased osteoclast numbers and enhanced in vivo bone resorption, whereas osteoblast numbers and in vivo bone-forming activity were unaffected. To understand the underlying cellular and molecular bases, we investigated ex vivo the differentiation of mutant bone marrow monocytes into osteoclasts and immune effectors, as well as osteoclastogenic signaling pathways. CIITA-overexpressing monocytes differentiated normally into effector macrophages or dendritic cells but showed enhanced osteoclastogenesis, whereas CIITA ablation suppressed osteoclast differentiation. Increased c-fms and receptor activator of NF-κB (RANK) signaling underlay enhanced osteoclast differentiation from CIITA-overexpressing precursors. Moreover, by extending selected phenotypic and cellular analyses to additional genetic mouse models, namely MHC Class II deficient mice and a transgenic mouse line lacking a specific CIITA promoter and re-expressing CIITA in the thymus, we excluded MHC Class II expression and T cells from contributing to the observed skeletal phenotype. Altogether, our study provides compelling genetic evidence that CIITA, the molecular switch of antigen presentation, plays a novel, unexpected function in skeletal homeostasis, independent of MHC Class II expression and T cells, by exerting a selective and intrinsic control of osteoclast differentiation and bone resorption in vivo. © 2014 American Society for Bone and Mineral Research.

Alkaline mineral water lowers bone resorption even in calcium sufficiency: alkaline mineral water and bone metabolism.

BACKGROUND: Dietary acid charge enhances bone loss. Bicarbonate or alkali diet decreases bone resorption in humans. We compared the effect of an alkaline mineral water, rich in bicarbonate, with that of an acid one, rich in calcium only, on bone markers, in young women with a normal calcium intake. METHODS: This study compared water A (per litre: 520 mg Ca, 291 mg HCO(3)(-), 1160 mg SO(4)(-), Potential Renal Acid load (PRAL) +9.2 mEq) with water B (per litre: 547 mg Ca, 2172 mg HCO(3)(-), 9 mg SO(4)(-), PRAL -11.2 mEq). 30 female dieticians aged 26.3 yrs (SD 7.3) were randomized into two groups, followed an identical weighed, balanced diet (965 mg Ca) and drank 1.5 l/d of the assigned water. Changes in blood and urine electrolytes, C-telopeptides (CTX), urinary pH and bicarbonate, and serum PTH were measured after 2 and 4 weeks. RESULTS: The two groups were not different at baseline, and showed a similar increase in urinary calcium excretion. Urinary pH and bicarbonate excretion increased with water B, but not with water A. PTH (p=0.022) and S-CTX (p=0.023) decreased with water B but not with water A. CONCLUSION: In calcium sufficiency, the acid calcium-rich water had no effect on bone resorption, while the alkaline water rich in bicarbonate led to a significant decrease of PTH and of S-CTX.

La viande et la santé publique [Meat and public health].

La presse a donné un large écho à une récente publication émanant du Centre international de recherche sur le cancer, une agence spécialisée de l'Organisation mondiale de la santé. Cette publication présente la reclassification de certains aliments carnés comme agents cancérigènes. Comme institution universitaire de santé publique, l'IUMSP souhaite apporter des précisions

Glucose-dependent insulinotropic polypeptide receptor deficiency leads to modifications of trabecular bone volume and quality in mice.

A role for the gastro-intestinal tract in controlling bone remodeling is suspected since serum levels of bone remodeling markers are affected rapidly after a meal. Glucose-dependent insulinotropic polypeptide (GIP) represents a suitable candidate in mediating this effect. The aim of the present study was to investigate the effect of total inhibition of GIP signaling on trabecular bone volume, microarchitecture and quality. We used GIP receptor (GIPR) knockout mice and investigated trabecular bone volume and microarchitecture by microCT and histomorphometry. GIPR-deficient animals at 16 weeks of age presented with a significant (20%) increase in trabecular bone mass accompanied by an increase (17%) in trabecular number. In addition, the number of osteoclasts and bone formation rate was significantly reduced and augmented, respectively in these animals when compared with wild-type littermates. These modifications of trabecular bone microarchitecture are linked to a remodeling in the expression pattern of adipokines in the GIPR-deficient mice. On the other hand, despite significant enhancement in bone volume, intrinsic mechanical properties of the bone matrix was reduced as well as the distribution of bone mineral density and the ratio of mature/immature collagen cross-links. Taken together, these results indicate an increase in trabecular bone volume in GIPR KO animals associated with a reduction in bone quality.

The effects of nutrition, puberty and dancing on bone density in adolescent ballet dancers.

Ballet dancers have on average a low bone mineral content (BMC), with elevated fracture-risk, low body mass index (BMI) for age (body mass index, kg/m2), low energy intake, and delayed puberty. This study aims at a better understanding of the interactions of these factors, especially with regard to nutrition. During a competition for pre-professional dancers we examined 127 female participants (60 Asians, 67 Caucasians). They averaged 16.7 years of age, started dancing at 5.8 years, and danced 22 hours/week. Assessments were made for BMI, BMC (DXA), and bone mineral apparent density (BMAD) at the lumbar spine and femoral neck, pubertal stage (Tanner score), and nutritional status (EAT-40 questionnaire and a qualitative three-day dietary record). BMI for age was found to be normal in only 42.5% of the dancers, while 15.7% had a more or less severe degree of thinness (12.6% Grade2 and 3.1% Grade 3 thinness). Menarche was late (13.9 years, range 11 to 16.8 years). Food intake, evaluated by number of consumed food portions, was below the recommendations for a normally active population in all food groups except animal proteins, where the intake was more than twice the recommended amount. In this population, with low BMI and intense exercise, BMC was low and associated with nutritional factors; dairy products had a positive and non-dairy proteins a negative influence. A positive correlation between BMAD and years since menarche confirmed the importance of exposure to estrogens and the negative impact of delayed puberty. Because of this and the probable negative influence of a high intake of non-dairy proteins, such as meat, fish, and eggs, and the positive association with a high dairy intake, ballet schools should promote balanced diets and normal weight and should recognize and help dancers avoid eating disorders and delayed puberty caused by extensive dancing and inadequate nutrition.

Predicting trabecular bone microdamage initiation and accumulation using a non-linear perfect damage model

Studies evaluating the mechanical behavior of the trabecular microstructure play an important role in our understanding of pathologies such as osteoporosis, and in increasing our understanding of bone fracture and bone adaptation. Understanding of such behavior in bone is important for predicting and providing early treatment of fractures. The objective of this study is to present a numerical model for studying the initiation and accumulation of trabecular bone microdamage in both the pre- and post-yield regions. A sub-region of human vertebral trabecular bone was analyzed using a uniformly loaded anatomically accurate microstructural three-dimensional finite element model. The evolution of trabecular bone microdamage was governed using a non-linear, modulus reduction, perfect damage approach derived from a generalized plasticity stress-strain law. The model introduced in this paper establishes a history of microdamage evolution in both the pre- and post-yield regions

Biofilm formation by staphylococci on fresh, fresh-frozen and processed human and bovine bone grafts.

Biofilm formation is a multi-step process influenced by surface properties. We investigated early and mature biofilm of Staphylococcus aureus on 4 different biological calcium phosphate (CaP) bone grafts used for filling bone defects. We investigated standardised cylinders of fresh and fresh-frozen human bone grafts were harvested from femoral heads; processed humanand bovine bone grafts were obtained preformed. Biofilm formation was done in tryptic soy broth (TSB) using S. aureus (ATCC 29213) with static conditions. Biofilm density after 3 h (early biofilm) and 24 h (mature biofilm) was investigated by sonication and microcalorimetry. After 3 h, bacterial density was highest on fresh-frozenandfresh bone grafts. After 24 h, biofilm density was lowest on freshbone grafts (p < 0.001) compared to the other 3 materials, which did not differ quantitatively (p > 0.05). The lowest increase in bacterial density was detected on fresh bone grafts (p < 0.001). Despite normal shaped colonies, we found additional small colonies on the surface of the fresh and fresh-frozen samples by sonication. This was also apparent in microcalorimetric heat-flow curves. The four investigated CaP bone grafts showed minor structural differences in architecture but marked differences concerning serum coverage and the content of bone marrow, fibrous tissue and bone cells. These variations resulted in a decreased biofilm density on freshand fresh-frozenbone grafts after 24 h, despite an increased early biofilm formation and might also be responsible for the variations in colony morphology (small colonies). Detection of small colony variants by microcalorimetry might be a new approach to improve the understanding of biofilm formation.

Pharmacological inhibition of interleukin-15 prevents colitis and associated bone loss in IL-10 knockout mice

Bone loss secondary to inflammatory bowel diseases (IBD) is largely explained by activated T cells producing cytokines that trigger osteoclastogenesis and accelerate bone resorptionwhile inhibiting bone formation. In IBD, elevated expression of interleukin (IL)-15, a T cell growth factor, plays a central role in T cell activation, pro-inflammatory cytokine production and the development of colitis. We previously reported that IL-15 enhances RANKL-induced osteoclastogenesis and that an IL-15 antagonist, CRB-15, prevents weight and bone loss in a mousemodel of dextran sulfate sodium-induced colitis.We hypothesized that inhibition of IL-15 signalingmight prevent bone loss in IL-10 deficient (IL10−/−) mice, that develop spontaneous bowel inflammation associatedwith osteopeniawhen they are no longer raised under germ-free conditions.Mice received anIL-15 antagonist (CRB-15, 5 μg/day, n=5) or IgG2a (5 μg/day, n=4) fromweek 10 to 14 of age. The severity of colitis was assessed by histology and bowel cytokine gene expression by real time PCR. Bone mass and architecturewere evaluated by ex vivo DXA on femur and micro-computed tomography on femur and vertebra. Bodyweight gainwas similar in the two groups. After 4 weeks, colonwas 29% shorter in CRB-15 treatedmice (p<0.006), a sign of reduced inflammation. Histological analysis indicated a transmural infiltration of inflammatory cells, lymphoepithelial lesions and increased size of villi (histological score=4/6) in IgG2a treated mice, whereas colon from CRB-15 treated mice exhibited mild infiltration of inflammatory cells of the lamina propria, no mucosal damages and a minimal increased size of villi (histological score=1.6/6). Levels of TNFα, IL-17 and IL-6 mRNA in the colon were significantly reduced in CRB-15 treated mice (p<0.04 vs IgG2), indicating a decrease in colon inflammation. CRB-15 improved femur BMD (+10.6% vs IgG2a, p<0.002), vertebral trabecular bone volume fraction (BV/TV, +19.7% vs IgG2a, p<0.05) and thickness (+11.6% vs IgG2a, p<0.02). A modest but not significant increase in trabecular BV/TV was observed at the distal femur. Cortical thicknesswas also higher at themidshaft femur in CRB-15 treatedmice (+8.3% vs IgG2a, p<0.02). In conclusion, we confirm and extend our results about the effects of CRB-15 in colitis. Antagonizing IL-15 may exert favorable effects on intestinal inflammation and prevent bone loss and microarchitecture alterations induced by colitis. This article is part of a Special Issue entitled ECTS 2011. Disclosure of interest: B. Brounais-Le Royer Grant / Research Support from Novartis Consumer Health Foundation, S. Ferrari-Lacraz: none declared, D. Velin: none declared, X. Zheng: none declared, S. Ferrari: none declared, D. Pierroz: none declared.

Strontium ranelate and alendronate have differing effects on distal tibia bone microstructure in women with osteoporosis.

The structural basis of the antifracture efficacy of strontium ranelate and alendronate is incompletely understood. We compared the effects of strontium ranelate and alendronate on distal tibia microstructure over 2 years using HR-pQCT. In this pre-planned, interim, intention-to-treat analysis at 12 months, 88 osteoporotic postmenopausal women (mean age 63.7 +/- 7.4) were randomized to strontium ranelate 2 g/day or alendronate 70 mg/week in a double-placebo design. Primary endpoints were changes in microstructure. Secondary endpoints included lumbar and hip areal bone mineral density (aBMD), and bone turnover markers. This trial is registered with http://www.controlled-trials.com, number ISRCTN82719233. Baseline characteristics of the two groups were similar. Treatment with strontium ranelate was associated with increases in mean cortical thickness (CTh, 5.3%), cortical area (4.9%) and trabecular density (2.1%) (all P < 0.001, except cortical area P = 0.013). No significant changes were observed with alendronate. Between-group differences in favor of strontium ranelate were observed for CTh, cortical area, BV/TV and trabecular density (P = 0.045, 0.041, 0.048 and 0.035, respectively). aBMD increased to a similar extent with strontium ranelate and alendronate at the spine (5.7% versus 5.1%, respectively) and total hip (3.3% versus 2.2%, respectively). No significant changes were observed in remodeling markers with strontium ranelate, while suppression was observed with alendronate. Within the methodological constraints of HR-pQCT through its possible sensitivity to X-ray attenuation of different minerals, strontium ranelate had greater effects than alendronate on distal tibia cortical thickness and trabecular volumetric density.

Are patterns of bone loss in anorexic and postmenopausal women similar? Preliminary results using high resolution peripheral computed tomography.

This study intended to compare bone density and architecture in three groups of women: young women with anorexia nervosa (AN), an age-matched control group of young women, and healthy late postmenopausal women. Three-dimensional peripheral quantitative high resolution computed-tomography (HR-pQCT) at the ultradistal radius, a technology providing measures of cortical and trabecular bone density and microarchitecture, was performed in the three cohorts. Thirty-six women with AN aged 18-30years (mean duration of AN: 5.8years), 83 healthy late postmenopausal women aged 70-81 as well as 30 age-matched healthy young women were assessed. The overall cortical and trabecular bone density (D100), the absolute thickness of the cortical bone (CTh), and the absolute number of trabecules per area (TbN) were significantly lower in AN patients compared with healthy young women. The absolute number of trabecules per area (TbN) in AN and postmenopausal women was similar, but significantly lower than in healthy young women. The comparison between AN patients and post-menopausal women is of interest because the latter reach bone peak mass around the middle of the fertile age span whereas the former usually lose bone before reaching optimal bone density and structure. This study shows that bone mineral density and bone compacta thickness in AN are lower than those in controls but still higher than those in postmenopause. Bone compacta density in AN is similar as in controls. However, bone inner structure in AN is degraded to a similar extent as in postmenopause. This last finding is particularly troubling.

Administration of Il-18bp by Gene Therapy Reduces Inflammation and Prevents Joint Destruction by Downregulation of Mmp9 In Rat Aia: Role ff Mmp9 In Bone and Joint Destruction in Arthritis

Background and objectives Interleukin 18 (IL-18) is a pleiotropic cytokine involved in rheumatoid arthritis (RA) pathogenesis. This study was carried out to evaluate the effi cacy of IL-18 binding protein (IL-18BP) gene therapy in the rat adjuvant- induced arthritis (AIA) model and to decipher the mechanisms by which IL-18BP delivery lessens bone destruction.Materials and methods Arthritis was induced in female Lewis rat by Mycobacterium butyricum and the mRNA expression of IL-18 and IL-18BP was determined in the joints. In a preventive study, rats were divided into an adenovirus producing IL-18BP-Fc (AdmIL-18BP-Fc) group (n=8) and an adenovirus producing green fl uorescent protein (AdGFP) group (n=7). On day 8 after AIA induction, adenoviruses were injected. Clinical parameters were assessed. At day 18, during maximal arthritis, the rats were euthanized, ankles were collected and x-rays were performed. mRNA and protein were extracted from joints for analysis by quantitative reverse transcriptase-PCR, multiplex, Western blot and zymography.Results The authors observed a decrease in the (IL-18BP/ IL-18) ratio from day 7 to 45. Administration of AdmIL-18BPd-Fc decreased clinical parameters and prevented bone and joint destruction compared to AdGFP administration. IL-18BP delivery reduced the (receptor activator of nuclear factor κB ligand (RANKL)/osteoprotegerin (OPG)) ratio by 70%, the matrix metalloproteinase 9 (MMP9) level by 33% and the tartrate-resistant acid phosphatase (TRAP) level by 44% in the joint homogenates from AdmIL-18BPd-Fc compared to AdGFP treated rats.Conclusions In rat AIA, a decrease in the (IL-18BP/IL-18) ratio was observed. IL-18BP delivery prevented joint and bone destruction by downregulating MMP9, (RANKL/OPG) and TRAP, suggesting a potential benefi t of a similar therapy in RA.Abstract topics Towards novel therapeutic strategies.

Meal-induced thermogenesis and obesity: is a fat meal a risk factor for fat gain in children?

Diet composition, in particular fat intake, has been suggested to be a risk factor for obesity in humans. Several mechanisms may contribute to explain the impact of fat intake on fat gain. One factor may be the low thermogenesis induced by a mixed meal rich in fat. In a group of 11 girls (10.1 +/- 0.3 yr), 6 obese (body mass index, 25.6 +/- 0.6 kg/m(2)), and 5 nonobese (body mass index, 19 +/- 1.6 kg/m(2)), we tested the hypothesis that a mixed meal rich in fat can elicit energy saving compared with an isocaloric and isoproteic meal rich in carbohydrate. The postabsorptive resting energy expenditure and the thermic effect of a meal (TEM) after a low fat (LF; 20% fat, 68% carbohydrate, and 12% protein) or an isocaloric (2500 kJ or 600 Cal) and isoproteic high fat (HF; 48% fat, 40% carbohydrate, and 12% protein) meal were measured by indirect calorimetry. Each girl repeated the test with a different, randomly assigned menu (HF or LF) 1 week after the first test. TEM, expressed as a percentage of energy intake was significantly higher after a LF meal than after a HF meal (6.5 +/- 0.7% vs. 4.3 +/- 0.4%; P < 0.01). The postprandial respiratory quotient (RQ) was significantly higher after a LF meal than after a HF meal (0.86 +/- 0.013 vs. 0.83 +/- 0.014; P < 0.001). The HF low carbohydrate meal induced a significantly lower increase in carbohydrate oxidation than the LF meal (20.3 +/- 6.2 vs. 61.3 +/- 7.8 mg/min; P < 0.001). On the contrary, fat oxidation was significantly higher after a HF meal than after a LF meal (-1.3 +/- 2.4 vs. -15.1 +/- 3.6 mg/min; P < 0.01). However, the postprandial fat storage was 8-fold higher after a HF meal than after a LF meal (17.2 +/- 1.7 vs. 1.9 +/- 1.8 g; P < 0.001). These results suggest that a high fat meal is able to induce lower thermogenesis and a higher positive fat balance than an isocaloric and isoproteic low fat meal. Therefore, diet composition per se must be taken into account among the various risk factors that induce obesity in children.

CD93 is required for maintenance of antibody secretion and persistence of plasma cells in the bone marrow niche.

Plasma cells represent the end stage of B-cell development and play a key role in providing an efficient antibody response, but they are also involved in numerous pathologies. Here we show that CD93, a receptor expressed during early B-cell development, is reinduced during plasma-cell differentiation. High CD93/CD138 expression was restricted to antibody-secreting cells both in T-dependent and T-independent responses as naive, memory, and germinal-center B cells remained CD93-negative. CD93 was expressed on (pre)plasmablasts/plasma cells, including long-lived plasma cells that showed decreased cell cycle activity, high levels of isotype-switched Ig secretion, and modification of the transcriptional network. T-independent and T-dependent stimuli led to re-expression of CD93 via 2 pathways, either before or after CD138 or Blimp-1 expression. Strikingly, while humoral immune responses initially proceeded normally, CD93-deficient mice were unable to maintain antibody secretion and bone-marrow plasma-cell numbers, demonstrating that CD93 is important for the maintenance of plasma cells in bone marrow niches.